Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Patent
1995-09-14
1996-08-06
Strecker, Gerard R.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
324371, G01V 324
Patent
active
055437150
ABSTRACT:
A method of determining resistivity of an earth formation penetrated by a wellbore having conductive casing. The preferred embodiment includes inserting a sonde into the wellbore, the sonde having a plurality of electrodes at axially spaced apart locations adapted to electrically contact the casing, applying electrical current between a first and a second one of the electrodes and measuring the current, measuring a first voltage between a first pair of electrodes axially disposed between the first and second electrodes and measuring a second voltage between a second pair of electrodes also axially disposed between the first and second electrodes and disposed externally to the first pair to determine casing resistance in between the pairs of electrodes. A second difference between the first and second voltages is also measured. Current is applied between other electrodes axially disposed to exclude a third pair of electrodes therebetween, and a third voltage is measured between the third pair to determine characteristic impedance. Current is applied between the first electrode and a surface return electrode, a fourth voltage is measured between the first pair of electrodes, a fifth voltage is measured between the second pair of electrodes, an additional second difference of voltages between the fourth voltage and the fifth voltage is measured, and formation resistivity is determined by combining the first voltage, the second voltage, the third voltage, the fourth voltage, the fifth voltage, the current measurements, the second difference and the additional second difference of the voltages.
REFERENCES:
patent: 2779912 (1957-01-01), Waters
patent: 2986693 (1961-05-01), Alder
patent: 3075141 (1963-01-01), Lamb
patent: 5075626 (1991-12-01), Vail, III
Fanini Otto N.
Maurer Hans M.
Singer Bension
Strack Kurt M.
Fagin Richard A.
Strecker Gerard R.
Western Atlas International Inc.
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